JPH09111127A - Curable silicone rubber composition, cured product therefrom, and semiconductor device sealed therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a curable silicone rubber composition having good flowability and giving a cured product excellent in heat conductivity and electrical insulation properties. SOLUTION: This composition comprises a diorganopolysiloxane containing at least two alkenyl groups in the molecule, an organohydrogenpolysiloxane containing at least two Sibonded hydrogen atoms in the molecule, a platinum group metallic catalyst, and a hexagonal boron nitride powder surface-treated with a vinyl or epoxy silane coupling agent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a curable silicone rubber composition capable of obtaining a cured product having excellent thermal conductivity and electrical insulation, the cured product and a resin-encapsulated semiconductor encapsulated with the cured product. Regarding the device.

[0002]

2. Description of the Related Art In recent semiconductor devices, the amount of heat generated by elements has become large due to the miniaturization of packages, the increase in speed, and the increase in chip size. What has excellent conductivity is desired. By the way, conventionally, hexagonal boron nitride powder has been known as a filler for imparting thermal conductivity or electrical insulation to a heat-dissipating silicone rubber sheet used for a power transistor or the like. It is also generally known that when the hexagonal boron nitride powder is mixed with the uncured silicone rubber composition, which is the raw material of the sheet, the viscosity of the composition increases and the fluidity deteriorates. Therefore, when the hexagonal boron nitride powder is added to the silicone rubber composition, the composition is usually an organic solvent such as benzene, toluene, xylene, pentane, heptane, hexamethylsilazane, diphenylsilanediol, cyclic dimethylsiloxane, etc. The above dispersant is blended together. However, since the silicone rubber composition containing such an organic solvent or dispersant foams during curing and has a high heating temperature for curing, so-called curing for semiconductor encapsulation used for coating and potting of semiconductor elements. It cannot be used as an acidic composition. In addition, particularly when used for the purpose of protecting a junction portion or a wire of a semiconductor element, reliability cannot be obtained if air bubbles are present.
In addition, the presence of bubbles is not preferable in terms of lowering thermal conductivity. That is, conventionally, even without the organic solvent or dispersant as described above, shows excellent fluidity, and contains sufficient hexagonal boron nitride powder to exhibit good thermal conductivity and electrical insulation. No curable silicone rubber composition has been obtained.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide excellent fluidity without containing an organic solvent or a dispersant, and to provide sufficient heat conductivity and electrical insulation. An object of the present invention is to provide an addition reaction-curable silicone rubber composition containing hexagonal boron nitride powder, a cured product thereof, and a resin-sealed semiconductor device sealed with the cured product.

[0004]

Means for Solving the Problems The first aspect of the present invention is that (A)
Diorganopolysiloxane containing at least two alkenyl groups in one molecule, (B) Organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms in one molecule, (C) Platinum group metal A curable silicone rubber composition comprising a system catalyst and (D) hexagonal boron nitride powder surface-treated with a silane coupling agent having a vinyl group or an epoxy group. The second aspect of the present invention is a cured product obtained by curing the composition.
A third aspect of the present invention is a resin-encapsulated semiconductor device obtained by encapsulating a semiconductor element with the cured product.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. (A) Alkenyl Group-Containing Diorganopolysiloxane The alkenyl group-containing diorganopolysiloxane used in the composition of the present invention contains at least two alkenyl groups in one molecule and usually has a main chain portion basically. It is generally composed of repeating diorganosiloxane units and has a straight chain structure in which both ends of the molecular chain are blocked with a triorganosiloxy group. Although it may have a structure or may be a cyclic body, a linear diorganopolysiloxane is preferable from the viewpoint of physical properties such as mechanical strength of the cured product. Even if the alkenyl group is present only at both ends of the molecular chain,
Alternatively, it may be present at both ends of the molecular chain and in the middle of the molecular chain. As a typical example of such an alkenyl group-containing diorganopolysiloxane, for example, the following general formula (1):

[0006]

Embedded image (Wherein, R ¹ is independently an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond, X is an alkenyl group, n is an integer of 0 or 1 or more, and m is Which is an integer of 0 or 1 or more).

In the formula, the unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond represented by R ¹ is, for example,
Methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group,
Alkyl groups such as neopentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl;
Cycloalkyl groups such as cyclopentyl group, cyclohexyl group and cycloheptyl group; aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group and biphenylyl group;
Benzyl group, phenylethyl group, phenylpropyl group,
An aralkyl group such as a methylbenzyl group; and a group in which part or all of the hydrogen atoms bonded to carbon atoms of these groups have been substituted with a halogen atom such as fluorine, chlorine, bromine, or a cyano group, for example, chloro Methyl group, 2-bromoethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6
6,6-nonafluorohexyl group and the like, a typical one having 1 to 10 carbon atoms, a particularly typical one having 1 to 6 carbon atoms, preferably a methyl group, An unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as an ethyl group, a propyl group, a chloromethyl group, a bromoethyl group, a 3,3,3-trifluoropropyl group, a cyanoethyl group, and a phenyl group, a chlorophenyl group, and a fluoro group. It is an unsubstituted or substituted phenyl group such as a phenyl group.

In the formula, the alkenyl group represented by X is, for example, a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, a hexenyl group, a cyclohexenyl group or the like, which usually has about 2 to 8 carbon atoms. Among them, lower alkenyl groups such as vinyl group and allyl group are preferable.

In the formula, n is 0 or an integer of 1 or more, and m is
Is 0 or an integer of 1 or more. Also, n and m are 10 ≦
It is preferably an integer satisfying n + m ≦ 10,000, more preferably 50 ≦ n + m ≦ 2,000, and 0 <m /
It is an integer satisfying (n + m) ≦ 0.2.

Such an alkenyl group-containing diorganopolysiloxane has a viscosity at 25 ° C. of 10 to 1,00.
It is preferable to use those having a cSt of about 000 cSt, especially about 100 to 500,000 cSt.

(B) Organohydrogen polysiloxy
The organohydrogenpolysiloxane used in the composition of the present invention contains at least two, preferably 3 or more per molecule.
Hydrogen atoms bonded to one or more silicon atoms (ie, SiH
And a resin having a linear, branched, cyclic, or three-dimensional network structure. Representative examples of such organohydrogenpolysiloxanes include, for example, the following average composition formula (2): H _a R ² _b SiO _{(4-ab) / 2} (2) (wherein R ² is independently a fat An unsubstituted or substituted monovalent hydrocarbon group containing no group unsaturated bond;
<A <2, 0.8 ≤ b ≤ 2 and 0.8 <a + b ≤ 3, and preferably 0.3 ≤ a ≤ 1, 1.5 ≤ b ≤ 2 and 1.
8 ≦ a + b ≦ 2.7).

In the formula, examples of the unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond represented by R ² include the same ones exemplified as R ^{1 in the} general formula (1). The typical ones have 1 to 10 carbon atoms, especially 1 to 7 carbon atoms, preferably a lower alkyl group having 1 to 3 carbon atoms such as a methyl group, a phenyl group, 3, 3
, 3-trifluoropropyl group. Examples of such organohydrogenpolysiloxanes include, for example, 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethyltetracyclosiloxane, 1,3,5,7, Siloxane oligomers such as 8-pentamethylpentacyclosiloxane; methylhydrogenpolysiloxane blocked with trimethylsiloxy groups at both ends of molecular chain, dimethylsiloxane / methylhydrogensiloxane copolymer blocked with trimethylsiloxy groups at both ends of molecular chain, silanol at both ends of molecular chain Group-blocked methyl hydrogen polysiloxane, molecular chain terminal silanol group-blocked dimethylsiloxane / methyl hydrogen siloxane copolymer, molecular chain terminal dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, molecular chain terminal dimethylhydrogensiloxy group-blocked Methyl hydrogen Polysiloxane with both molecular chain terminals blocked with dimethylhydrogensiloxy groups dimethylsiloxane-methylhydrogensiloxane copolymers; R ₂ (H)
It consists of SiO _1/2 units and SiO _4/2 units, and optionally R ₃
SiO _1/2 unit, R ₂ SiO _2/2 unit, R (H) SiO
_A silicone resin which may contain _2/2 units, (H) SiO _3/2 units or RSiO _3/2 units, wherein R is an unsubstituted or substituted monovalent hydrocarbon group exemplified as R ¹ above. And the like; and the following formula:

[0013]

Embedded image And the like.

The organohydrogenpolysiloxane used in the composition of the present invention can be obtained by a known method, for example, the following general formulas: R ² SiHCl ₂ and R ² ₂ SiHCl (wherein R ² is as described above). Are the same), or at least one chlorosilane selected from the following general formulas: R ² ₃ SiCl and R ² ₂ SiCl ₂ wherein R ² is the same as above. It can be obtained by combining and hydrolyzing at least one selected chlorosilane. Further, the organohydrogenpolysiloxane may be one obtained by equilibrating the polysiloxane obtained by co-hydrolysis in this manner.

The amount of the component (B) used is such that the hydrogen atom in the organohydrogenpolysiloxane of the component (B) is usually 0.5 per mol of vinyl group in the vinyl group-containing diorganopolysiloxane of the component (A). The amount is -4 mol, preferably 1-2.5 mol.

(C) Platinum Group Metal-Based Catalyst The platinum group metal-based catalyst used in the present invention is the above-mentioned component (A).
Is a catalyst for accelerating the addition reaction between the vinyl group of (4) and the hydrogen atom bonded to the silicon atom of component (B), and a well-known catalyst can be used as the catalyst used in the hydrosilylation reaction. Specific examples thereof include platinum (including platinum black), rhodium, palladium, and other platinum group metal simple substances; H ₂
PtCl ₄ · nH ₂ O, H ₂ PtCl ₆ · nH ₂ O, N
aHPtCl ₆ · nH ₂ O, KHPtCl ₆ · nH
₂ O, Na ₂ PtCl ₆ · nH ₂ O, K ₂ PtCl ₄ ·
nH ₂ O, PtCl ₄ · nH ₂ O, PtCl ₂ , Na ₂
Platinum chloride such as HPtCl ₄ .nH ₂ O (wherein n is an integer of 0 to 6, preferably 0 or 6);
Chloroplatinic acid and chloroplatinate; Alcohol-modified chloroplatinic acid (see US Pat. No. 3,220,972); Complex of chloroplatinic acid and olefin (US Pat. No. 3,159,601) Same 3,159,662
No. 3,775,452); a platinum group metal such as platinum black or palladium is alumina, silica,
Supported on a carrier such as carbon; rhodium-olefin complex; chlorotris (triphenylphosphine) rhodium (Wilkinson catalyst); platinum chloride, chloroplatinic acid or chloroplatinate and vinyl group-containing siloxane, especially vinyl group-containing cyclic Examples thereof include complexes with siloxane.

The amount of the component (C) used may be a so-called catalytic amount, and is usually 0.1 to 500 ppm, particularly 0.5 to 0.5 ppm in terms of the weight of the platinum group metal based on the total amount of the components (A) and (B).
It may be about 200 ppm.

(D) Hexagonal Boron Nitride Powder The hexagonal boron nitride powder used in the present invention is surface-treated with a silane coupling agent containing a vinyl group or an epoxy group. The hexagonal boron nitride powder surface-modified with the silane coupling agent as described above provides a cured product of the composition with thermal conductivity and electrical insulation while appropriately maintaining the fluidity of the silicone rubber composition containing the powder. Imparts sex.

Silane Coupling Agent Containing Vinyl Group or Epoxy Group The silane coupling agent is not particularly limited as long as it is a silicon compound having a vinyl group or an epoxy group. For example, the following general formula (3): SiR ³ _i R ⁴ _j R ⁵ _k (3) (In the formula, R ³ is a vinyl group or a monovalent organic group containing an epoxy group, and R ⁴ is a monovalent hydrolyzable group or a hydrolyzable atom. R ⁵ is an alkyl group, i is 1 to 3
Is an integer of 1 to 3, and j is an integer of 1 to 3, preferably 2 or 3.
And k is an integer of 0-2. However, i + j + k =
4)).

In the formula, the monovalent organic group containing an epoxy group represented by R ³ is, for example, Z- (CH ₂ ) _p- (wherein Z is

[0021]

Embedded image And p is an integer of 0 to 4), specifically, for example, 3,4-epoxycyclohexyl group, 3,4-epoxycyclohexylalkyl group, glycidyl group , Glycidoxy groups, glycidoxyalkyl groups, especially γ-glycidoxypropyl groups, β- (3,
4-epoxycyclohexyl) ethyl group and the like.

In the formula, the monovalent hydrolyzable group or hydrolyzable atom of R ⁴ is, for example, methoxy group, ethoxy group,
Butoxy group, propoxy group, isopropoxy group, and other alkoxy groups; β-methoxyethoxy group, β-ethoxyethoxy, and other alkoxyalkyloxy groups; chlorine atom, dimethylketoxime group, methylethylketoxime group, and other ketoxime groups; acetoxy group , An acyloxy group such as a propionoxy group; an alkenyloxy group such as an isopropenyloxy group and an isobutenyloxy group.

In the formula, the alkyl group represented by R ⁵ is, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group or heptyl group. , Octyl group, nonyl group, decyl group, dodecyl group and the like, which usually have about 1 to 10 carbon atoms.

Specific examples of such a silane coupling agent include, for example, the following formulas: Cl ₃ SiCH = CH ₂ , (CH ₃ O) ₃ SiCH = C
_{H 2, (C 2 H 5} O) 3 SiCH = CH 2, (CH 3 O
C ₂ H ₄ O) ₃ SiCH = CH ₂ ,

[0025]

Embedded image And the like.

Hexagonal Boron Nitride Powder As the hexagonal boron nitride powder to be subjected to the surface treatment, known ones can be used, and usually, the average particle size may be about 1 to 30 μm, and the average particle size is preferably 5 ~ 20 μm
belongs to. If the average particle diameter is too small, the aggregated particles may increase and it may be difficult to uniformly disperse the particles in the composition. In addition, when the composition is cured, a large amount of hexagonal boron nitride grain boundaries are generated in the cured product, and sufficient heat radiation characteristics may not be obtained. On the contrary, if the average particle size is too large, the surface of the cured product may not be smooth and unevenness may occur on the surface. The hexagonal boron nitride powder preferably has a purity of boron nitride (before surface treatment) of 95% by weight or more, particularly 98% by weight or more. If the purity is too low, when the composition containing the powder is cured, the thermal conductivity and the electrical insulation of the cured product may be reduced due to the influence of impurities in the powder. Further, it is preferable that the hexagonal boron nitride powder has developed crystallization,
Preferably, the Lc value measured in accordance with the Gakushin Carbon Material 117 Committee Law is 500 ° or more, particularly 700 ° or more.
In addition, in a composition containing a so-called amorphous powder having an Lc value that is too small, the cured product obtained may have insufficient thermal conductivity and electrical insulation.

Surface Treatment As the surface treatment method, a known wet treatment method or dry treatment method can be used. As a specific example of such a surface treatment method, for example, after dissolving the silane coupling agent in alcohol, water and acetic acid and a hydrolysis catalyst such as Sn are added to the solution, and then the hexagonal crystal is added. A method may be mentioned in which boron nitride powder is blended, mixed, and then dried. Examples of the alcohol include methanol, ethanol, isopropyl alcohol, butanol and the like. The amount of the silane coupling agent used can be appropriately adjusted according to the specific surface area of the hexagonal boron nitride powder and other properties, but is usually about 0.1 to 10 parts by weight per 100 parts by weight of the hexagonal boron nitride powder. Good.
By such surface treatment, a siloxane coating containing a vinyl group or an epoxy group is formed on the surface of the hexagonal boron nitride powder. The hexagonal boron nitride powder having this siloxane coating has excellent affinity with organopolysiloxanes such as component (A) and component (B). Therefore, the curable silicone rubber composition containing the surface-treated hexagonal boron nitride powder has a low viscosity and excellent flowability as compared with the composition containing the untreated surface.

The amount of the surface-treated hexagonal boron nitride powder used is usually 30 to 300 parts by weight, preferably 80 to 200 parts by weight, per 100 parts by weight of the alkenyl group-containing diorganopolysiloxane of component (A). . If the amount is too small, the heat conductivity and electrical insulation of the obtained cured product may be insufficient.If the amount is too large, the viscosity of the obtained curable silicone rubber composition increases and the fluidity increases. May worsen.

Other Components In addition to the components (A), (B), (C) and (D), the composition of the present invention may optionally contain, for example, fumed silica or fumed dioxide. Reinforcing inorganic fillers such as titanium; calcium carbonate, calcium silicate,
Non-reinforcing inorganic fillers such as titanium dioxide, ferric oxide and carbon black can be added. The amount of the inorganic filler to be used is usually 0 to 200 parts by weight per 100 parts by weight of the total amount of the components excluding the inorganic filler.

Curable silicone rubber composition and its curing
The composition of the present invention contains the above- mentioned components such as Component (A) and Component (C), and Component (B) and Component (D) in the same manner as a usual curable silicone rubber composition.
It may be a so-called two-liquid type composition which is divided into liquids and is mixed and cured when used. Further, a so-called one-pack type composition in which the above-mentioned components are mixed and a small amount of a curing inhibitor (eg, acetylene alcohol) is added to the composition may be used. For the purpose of improving the adhesiveness of the composition, an epoxy group-containing polysiloxane compound or an ester siloxane compound may be added, if necessary, in addition to the above components. The composition of the present invention thus obtained has good flowability. The cured product of the present invention is obtained by curing the composition. The curing conditions may be the same as those of a known addition reaction-curable silicone rubber composition. For example, the composition may be sufficiently cured at room temperature, but may be heated if necessary. Such a cured product of the present invention is excellent in thermal conductivity and electrical properties.

Resin- Encapsulated Semiconductor Device The semiconductor device of the present invention is obtained by encapsulating a semiconductor element with a cured product of the curable silicone rubber composition of the present invention. Such a semiconductor device can be manufactured by a known method, and for example, can be obtained by coating or potting a predetermined portion of a semiconductor element using a curable silicone rubber composition and curing the composition. it can. Examples of the semiconductor element include integrated circuits, transistors,
A thyristor, a diode, and the like can be used, but they are not particularly limited. Such a semiconductor device of the present invention is excellent in heat dissipation and electrical insulation.

[0032]

The present invention will be described more specifically below with reference to examples and comparative examples. Example 1 A solution of 2 parts by weight of γ-glycidoxypropyltrimethoxysilane in 50 parts by weight of methanol was added to 100 parts of water.
Then, 20 parts by weight of a 60% by weight aqueous acetic acid solution were sequentially mixed. Next, this mixture was subjected to ultrasonic vibration for 1 hour to prepare a silane solution. Hexagonal boron nitride powder [KBN (h) -10 manufactured by Shin-Etsu Chemical Co., Ltd.] was added to this silane solution.
(Brand name), average particle size: 10 μm, purity: 99.7%, Lc
Value: 1000 Å or more] 100 parts by weight was added and mixed in a planetary mixer for 3 hours, and then the mixture was dried in a vacuum at 130 ° C. for 10 hours to obtain a surface-treated hexagonal boron nitride powder. Then the following formula:

[0033]

Embedded image (In the formula, n is the viscosity of the siloxane at 25 ° C. is 40
And a hexagonal boron nitride powder after the surface treatment described above, and 100 parts by weight of a linear dimethylpolysiloxane whose both molecular chain ends are blocked with dimethylvinylsilyl groups. 100 parts by weight of the powder was mixed with a planetary mixer for 1 hour, and then kneaded with three rolls. Next, this kneaded material was mixed with methyl hydrogen siloxane (content of hydrogen atoms bonded to silicon atoms: 0.8
Mol / 100 g) 5.1 parts by weight and octyl alcohol modified solution of chloroplatinic acid (platinum content 2% by weight) 0.02
The parts by weight were added and stirred to obtain a curable silicone rubber composition. The viscosity of the composition was measured using a B-type rotational viscometer and found to be 21000 cP. Next, 1 part of the composition
It was poured into a mold of 50 mm × 100 mm × 2 mm, degassed under vacuum, and then heated at 150 ° C. for 4 hours to obtain a sheet-shaped cured product. The obtained cured product was measured for thermal conductivity, volume resistivity, dielectric breakdown voltage, dielectric constant and dielectric loss tangent according to the following criteria. Table 1 shows the results.

Thermal conductivity [λ: (cal / (cm · sec · ° C)] A test piece with a diameter of 5.0 mm and a thickness of 9 mm was used as an upper heater plate (low temperature side).
And crimp between the lower heater plate (heating side). After the temperature becomes constant, the temperature difference between both sides of the heat-dissipating silicone rubber and the heat flow rate Q / A [where Q is the amount of power transmission (cal / sec), A
Is the cross-sectional area (cm ² ) of the test piece] and calculated from the following formula.

[0035]

(Equation 1) [In the formula, Q and A are the same as above, L is the length (cm) of the test piece, and ΔT is the temperature difference (° C) between the two surfaces of the test piece]

Volume resistivity Measured according to JIS C 2123.

Dielectric breakdown voltage Measured according to JIS C 2123.

Dielectric constant was measured according to JIS C 2123.

The dielectric loss tangent was measured according to JIS C 2123.

Example 2 A curable silicone was prepared in the same manner as in Example 1 except that 2 parts by weight of vinyltris (β-methoxyethoxy) silane was used in place of γ-glycidoxypropyltrimethoxysilane. A rubber composition was obtained. The viscosity of the composition was measured using a B-type rotational viscometer and found to be 26400 c
P. The thermal conductivity, volume resistivity, dielectric breakdown voltage, dielectric constant and dielectric loss tangent of the cured product obtained in the same manner as in Example 1 were measured in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 In Example 1, instead of the surface-treated hexagonal boron nitride powder powder, the surface-treated hexagonal boron nitride powder [Shin-Etsu Chemical Co., Ltd. KBN (h)-] was used. 10 (supra)] A curable silicone rubber composition was obtained in the same manner as in Example 1 except that 100 parts by weight was used. The composition comprises:
It has high viscosity and high thixotropy, and the viscosity of the composition was measured using a B-type rotational viscometer.
Met. Further, in the same manner as in Example 1, the composition was poured into a mold and vacuum defoaming was attempted, but it was difficult to sufficiently defoam. Therefore, toluene was added to the composition to dilute (content of the composition: 50% by weight), and then defoamed.
Then, after the toluene contained in the composition is scattered, 1
It was heated at 50 ° C. for 4 hours to obtain a sheet-like cured product. The obtained cured product was measured for thermal conductivity, volume resistivity, dielectric breakdown voltage, dielectric constant and dielectric loss tangent in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 Example 1 was repeated except that 2 parts by weight of N- (β-aminoethyl) γ-aminopropyltrimethoxysilane was used instead of γ-glycidoxypropyltrimethoxysilane. A curable silicone rubber composition was obtained in the same manner as. As a result of measuring the viscosity of the composition using a B type rotational viscometer, it was 37,000 cP. And Example 1
An attempt was made to cure the composition in the same manner as in 1. but the composition did not cure due to the catalytic poisoning effect of the amino group.

Comparative Example 3 A curable silicone was prepared in the same manner as in Example 1 except that 2 parts by weight of γ-methacryloyloxypropyltrimethoxysilane was used in place of γ-glycidoxypropyltrimethoxysilane. A rubber composition was obtained. As a result of measuring the viscosity of the composition using a B type rotational viscometer,
It was 49000 cP. The thermal conductivity, volume resistivity, dielectric breakdown voltage, dielectric constant and dielectric loss tangent of the cured product obtained in the same manner as in Example 1 were measured in the same manner as in Example 1. Table 1 shows the results.

[0044]

[Table 1]

Evaluation As shown in Table 1, the composition of the present invention (see Examples 1 and 2) is compared with a composition containing hexagonal boron nitride powder which is not surface-treated (see Comparative Example 1). The viscosity is extremely low and the fluidity is excellent. Also the thermal conductivity after curing,
The electrical characteristics are also good. Further, the composition containing the hexagonal boron nitride powder surface-treated with the silane coupling agent other than the component (D) of the present invention (see Comparative Examples 2 and 3) has a small decrease in viscosity, and particularly contains an amino group. In the composition using the silane coupling agent (see Comparative Example 2), curing inhibition was caused by the catalytic poisoning action.

[0046]

The composition of the present invention has good fluidity, and the cured product of the present invention has excellent heat conductivity and electrical insulation. Further, the resin-encapsulated semiconductor device of the present invention is excellent in heat dissipation and electrical insulation.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuichi Washio 2-13-1, Isobe, Annaka City, Gunma Prefecture Shin-Etsu Kagaku Kogyo Co., Ltd., Institute for Precision Materials (72) Toshihiko Shindo Annaka City, Gunma Prefecture 2-13-1 Isobe Shin-Etsu Chemical Co., Ltd. Precision Materials Research Laboratory

Claims (3)

[Claims] 1. (A) a diorganopolysiloxane containing at least two alkenyl groups in one molecule, (B) an organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms in one molecule. A curable silicone rubber composition comprising siloxane, (C) a platinum group metal-based catalyst, and (D) a hexagonal boron nitride powder surface-treated with a silane coupling agent containing a vinyl group or an epoxy group. 2. A cured product obtained by curing the composition according to claim 1. 3. A resin-sealed semiconductor device in which a semiconductor element is sealed with the cured product according to claim 2.